Field of the Invention
The present invention relates to a method and an apparatus for processing control signals in a mobile station of a mobile radio station, where control signals are received from one current base station and from other base stations.
Methods and apparatus of that type are generally known from the prior art. In mobile radio systems, such as GSM (Global System for Mobile Communications), PCN (Personal Communication Network), PCS (Personal Communication System) and DECT (Digital European Cordless Telephone) systems, and so forth, control signals from the base station of the cell in which the mobile stations are located and from the base stations of other, for instance adjacent cells, are received at regular intervals by the mobile stations, especially when they are in the idle mode. For instance, in the GSM system, a mobile station in the idle mode regularly measures the reception field intensity or reception level of the BCCH channels (Broadcast Control Channels) from up to 32 different base stations.
The BCCH is unidirectional from the respective base stations to the mobile station. Each cell of a mobile radio network is assigned one base station, which supplies the region of the cell with BCCH information. If a mobile station, such as a mobile phone, is registered in the mobile radio network, then in addition to the BCCH information it receives other information relating to whether a call for that mobile station is present. The better the reception quality, the better can the mobile station decipher this information, and the higher the availability and accessibility of the mobile station.
In the GSM system, for instance, it is the task of the applicable mobile station to listen to precisely that cell or base station from which it expects the best reception quality. The best criterion for the reception quality is the reception level of the receive signals. Therefore, at those times at which the mobile station is not receiving any BCCH information from the current base station in the cell where it is located, the mobile station measures the reception level of control signals, such as BCCH signals, of adjacent base stations. After that, the mobile station compares the reception level of the control signals of the adjacent, other base stations with the reception level of the control signals or BCCH signals of the current base station. If the mobile station ascertains that the reception level of the control signals of another base station is higher than the reception level of the control signals of the current base station, then it switches over to the base station, whose control signals are at a higher level. The faster the base station detects these different levels, the better the accessibility.
On the one hand, it is accordingly a goal to measure the reception levels of the control signals of the other base stations as often as possible; on the other hand, each time this consumes power in the mobile station for receiving the control signals of the other base station or measuring its reception level, since the receiving device of the mobile station must be turned on during this time period. The two goals of low current consumption and optimal reception quality or accessibility of the mobile stations are thus mutually contradictory. As already noted above, in conventional mobile stations, comparisons of the reception levels of the control signals of the current base station with the reception levels of the control signals of other, adjacent base stations are performed at regular time intervals. These comparisons are performed even when the mobile station is not in motion, which makes for unnecessary current consumption in the mobile stations. This is particularly disadvantageous if the mobile station is battery-operated.